PET, or polyethylene terephthalate, is the most important member of the thermoplastic polyester family. Its English name is Polyethylene terephthalate, abbreviated as PET or PEIT (hereafter referred to as PET), and it is commonly known as polyester resin. It is a condensation polymer of terephthalic acid and ethylene glycol. Together with PBT, it is collectively classified as thermoplastic polyester, or saturated polyester. In flexible plastic packaging, PET typically has a thickness of 12 microns and is used as an outer layer; its surface can be metallized with aluminum, or it may serve as an intermediate layer. As a key component in packaging applications, PET is favored for its unique properties and advantages.

1. It exhibits excellent mechanical properties, with high impact strength and good flexural resistance. It is suitable for vacuum packaging.
2. Resistant to oils, fats, dilute acids and dilute alkalis, and to most solvents. Suitable for food packaging, liquid packaging, detergent packaging, and packaging for grains and oils.
3. Pure PET has limited heat resistance, with a heat deflection temperature of only about 85°C; however, its thermal performance improves significantly after reinforcement. It is microwave‑safe and suitable for steaming or boiling. Nevertheless, it is not recommended for freezing, as it becomes brittle at low temperatures.
4. It exhibits low gas and water vapor permeability, providing excellent barrier properties against gases, moisture, oils, and odors.
5. High transparency, UV‑blocking, and excellent gloss.
6. Non-toxic, odorless, and highly safe for health; suitable for direct use in food packaging.